Over heating

Post by **beal1982** » Mon May 04, 2009 9:31 pm

We've been away for the weekend and have travelled almost 400 miles, whilst on our journey we experienced some over heating on the m25, we called the aa who knocked out the thermostat which appeared to cure all probelms.However,On the journey home i found the overflow on the radiator had again been over flowing. I'm pretty confident it is not a head gassket as there is no visible signs from the exhaust or oil/water, there is no leaks within the system, and the pump appears to be working as normal.any ideas of where to start,? i'm thinking of replacing the radiator cap as that may be faulty( cheapest first).Any suggestions would be gratefully received.

Post by **alanworland** » Mon May 04, 2009 9:48 pm

Replace cap and try again, then I would try a radiator out and flush/backflush - might be silted up

Post by **bmcecosse** » Mon May 04, 2009 9:53 pm

Was it actually boiling up when it overheated ?? It is NOT a good idea to run without a thermostat - ok for a 'get home fix' - but do not run the engine like that. By all means try a new stat (~ 72 degree for summer) and a new cap - but then fill the rad to the top and run the engine at idle. If regular stream of bubbles appear - not just initial trapped air - then it will be head gasket. If no bubbles - well a good flushing won't do any harm and may very well solve the problem.

Post by **beal1982** » Mon May 04, 2009 10:06 pm

It was boiling over.

Post by **bmcecosse** » Mon May 04, 2009 10:14 pm

Hmmm - not good. Would expect that to have cleared out any gunge!

Post by **downsey** » Mon May 04, 2009 10:34 pm

Just out of curiosity, what are the ill effects of running without a thermostat bmc?

Post by **bmcecosse** » Mon May 04, 2009 11:05 pm

Water short circuits around the front of the engine only - rear cylinders overheat. And of course - if only gentle running the whole engine is over-cooled (ok maybe not in San Jose!) - mayo in rocker cover/high moisture content in oil - and general inefficient running!
For competition use (where no risk of cool running) - a thermostat blanking sleeve can be fitted to ensure good circulation around the whole engine.

Post by **sirrom** » Tue May 05, 2009 7:00 am

I had to replace a frost plug recently as it was weeping so did them all but was surprised that when I got the plugs out there was solid mass behind them and also found that it wouldnt drain from the rear water tap. In the end I took the head off and water blastered down the water jackets and into the rear drain hole under the manifold. Was really surprised how much stuff came out and then wondered how the water was circulating. Another engine which I rebuilt that was the first thing I did when I had it down to a bare block to clean it. It surprising how much clug can be trapped at the rear of the block.

Post by **bmcecosse** » Tue May 05, 2009 7:29 am

Aye - a good clean out can work wonders. Some use drain cleaner in the rad - but there are specialist products available.

Post by **beal1982** » Tue May 05, 2009 8:15 pm

I've just flushed out the radiator and ran the car at idle for 20 mins with no problems. Don't think its the h gasket as there are no bubbles and the hoses are not hard.

Post by **bmcecosse** » Tue May 05, 2009 9:41 pm

Good luck!